Spark-gap indicator



T. F. JOHNSON, Jn.

SPARK GAP INDICATOR.

APPLICATION FILED ]AN.12, 1920.

1,347,378, Patented July 20, 1920.

ffi'cfoiuw'am qfn, INVENTOR/ WITNESSES /W/MQ M & BY. E!

ATTORN IY TOMLINSON F, JOHNSON, m, OFATLANTA, GEORGIA.

SPARK-GAP INDICATOR.

Specificationof Letters Patent. 1 Patented July 20, 1920- Application filed January 12, 1920. "Serial No. 350,764.

To all whom it may concern:

Be it known that I, ToMLrNsoN F. J OHN- SON, Jr., a citizen of the United States, residing at Atlanta, in the county of Fulton and State of Georgia, have invented a new and useful Spark-Gap Indicator, of which the following is a specification.-

This invention has reference to spark-gap indicators, and its object is to automatically give sensible indication of a weakening or break-down in the insulators of high tension alternating current transmission lines, thus avoiding the necessity of testing out all of the insulators on the line.

The invention comprises a spark-gap ar ranged. inseries with a stack or string of insulators, consisting of alternately-placed insulating and conducting, or semi-conduct.

ing material, and the ground side of the string or stack. This spark gap, placed in series between the stack or string of insulators and the ground, 18 so set as not to fire.

so long as the insulating units comprising the string or stacks are good, but should one or more of the insulatorsof the string become defective to any material extent, the spark will strike across the gap, making a sufficient noise tobe heard to a considerable distance or. to otherwise givea clear indication ofa defect.

By placing the gap between the string of insulators and the ground, it is located in a position where, as a rule, there is but low,

voltage to be carried by thespark gap insulator, wherefore its form may be materially different from a regular line insulator, thus making it cheaper to build and of a more permanent nature- While the 10- a cation of the spark gap between one end of a string of insulators and the ground has certain advantages, such location is not obligatory, since, by properly designing the spark gap, it maybe placed at any point along the string.

The inventionwill be best understood lrom a consideration of the following detailed description taken inconnection with the accompanying drawing forming part of this specification, with the understanding, however, that the invention is not con fined to any strict conformity with the showing in the drawing, 1 but may be changed and modified so long as] such changes and modifications mark no material departure from thesalientfeatures of the invention as expressed in the appended claims.

In; the drawings,

Figure 1 is an elevation of a string or stack of suspension insulators interposed between a line wire and a cross arm or other support, with a spark gapin series with the string of insulators.

Fig. 2 is an elevation of a pin type insulator provided with a spark gap in series with the conductor, insulator and support.

Fig. 3 is a central vertical section of the structure shown in Fig. 2.

Referring to the drawing, and especially to Fig. 1, there isshown a cross arm or beam 1, or. other support such as is used in high tension transmission lines. There is also shown a line Wire 2 which may be containing the line wire 2, which may be assumed tobe charged, is shown a string of insulators 3 of the customary suspension type or of other suitable type, hence requiring no special description.

lnterposed between the cross arm 1 and the first one of the string of insulators carrying the line conductor 2, is a block 1 of insulating material with heads 5 and 6, which may be of metal, connected to the insulator block 4 and sustaining the entire string of insulators 3. Each head 5 and 6 carries a metal rod or pin 7 with a terminal 8 which -may also be of metalin the form of a ball. The terminals 8 are brought intosuch close relation as to provide an air gap capable of: being jumped by the current. string of insulators in perfect condition or only iinmaterially defective, no spark will pass across the air gap, but should the in- 9 sulating qualities of the string of insulators The air gap. is such. that with the become materially weakened, a spark or so that at the cross arm 1 thejelectrical pressure may be considered as zero or negligibly near to zero and at any rate as too small to 'ause sparks to pass across the gap between the terminals 8. On such high volt-agelines, it frequently occurs that the insulating units are unable to withstand the pressure and one or more will weaken or break down. Such weakening of the insulating qualities of the insulators may be quite material but too small to produce a visible or audible dis charge with insulators as ordinarily constructed. However, with the invention applied a relatively small weakening of the insulating qualities is sufficient to cause the passag; ot' sparks between the terminals 8 and consequently notice to be given to an observer that the string of insulators requires attention to ascertain the particular insulator units which may be defective so that the string of insulators may be restored to the proper condition. Such notice of defects will usually be given long before the leakage becomes serious, so that repairs may be made without great loss of current.

It has heretofore been the custom to test out the insulators from time to time, such operation requiring workmen to climb the poles or towers carrying the lines and test or feel out the strings or other types of insulators, after which, if the testing-out pro cedure shows it to be safe to the workmen, the individual insulator units are tested to positively select those which have actually broken down and which need replacing. In accordance with the prior custom, every group of insulator units had to be tested. thus consuming a great deal of time and on long lines requiring practically the entire time of workmen assigned to such service.

\Vith the present invention, a single work man traveling along the ground may quickly pickout or spot those insulators giving evidence of defect, and by marking or otherwise indicating the defective insulators, will thus save the necessity of testing any of the insulators except those automatically showing the presence of a defect, leaving relatively few of the insulators to be tested out for replacements.

In the structure shown in Figs. 2 and 3, there is shown a cross arm or supporting part 9 of a mast or other supporting structure such as is employed in high tension transmission lines, and this cross arm carries a pin 10 having an insulating section 11 and a conducting or semi-conducting section 12, the latter terminating in a screwthreaded extremity 13, such extremity being usually coarsely threaded.

Mounted on the screw-th *eaded end 13 of the pin 10 in pendent relation thereto and nesting more or less in each other are skirts ll. 15. 16. of insulating material, say porcelain. Three such skirts are shown, but

it is to be understood that a greater or less number may be used. The uppermost skirt has an expanded top lishaped to form a cradle in which a conductor 2 like the conductor 2 of Fig. 1, rests and is held by wire anchor 18, as is customary.

Fast to a ring or support 19 carried by the cross arm 9 is a stem 20 ending in a ball 21 or other suitable terminal, and connected to and extending from the conducting or semi-conducting continuation of the pin 10 is another stem 22 ending in a ball 23 or other suitable terminal in appropriate striking distance of the terminal 21, whereby the two balls 21 and 23 deiine a spark gap like that defined between the two balls or terminals 8.

The conditions between the spark gap terminals 21 and 23 are similar to those between the spark gap terminals 8, so that while current is flowing over the line conductor 2, a difference of potential, with all the parts in perfect condition, is established between the terminals 21 and 23 but insuilicient in intensity to cause a spark to strike across the spark gap. breaking down or the lessening of the resisting qualities'of the insulator of Figs. 2 and 35, there is a corresponding increase in the difference of potential between the terminals 21 and 23, the conductor 2 being energized as usual. As soon as the difference of potential is sufliciently great, sparks will pass between the terminals 21 and 23, thus giving evidence of the weakening of the resisting qualities of the insulator and thereby giving warning to an observer that the insulator needs replacing. The action of the pi'n like insulator of Figs. 2 and 3'is substantially the same as that of the string insulator of Fig. 1.

In application Serial No. 318,025, fi1ed by me on August 16, 1919, there is shown and described a spark-gap indicator by which automatic audible or visible indications are given of defects in the insulators, but in the said application the spark gap arrangement is such that it may be termed a multiple or parallel gap arrangement, while in this case the gap is in series with the insulators, wherefore it may be termed a series arrangement of the gap and insulators.

What is claimedisz- 1. In a high tension alternating current transmission line, an insulator for supporting the line conductor having a series spark gap between the line conductor and ground.

2. In a high tension alternating current transmission line, an insulator't'or supporting the line conductor having a series spark gap between the line conductor and ground, the spark gap being located on the ground side of the insulatoras a whole.

3. In a high tension alternating current transmission line, an insulatorfor the line In the event of the conductor, insulating means at the ground end of and carrying the insulator, and a spark gap around the insulating means carrying the insulator and set to pass sparks at a predetermined diminution of the resistance of the main insulator. p

4. A high tension alternating current transmission line provided with insulators for supporting the line conductor, each insulator having a permanent spark gap in series therewith and set to remain silent under normal conditions of transmission and to sensibly respond to a lessening of the insulating qualities of the insulator as a whole.

5. A high tension alternating current transmission line provided with insulators for supporting the line conductor and each comprising a plurality of insulating units, and a permanent spark gap included in series with the plurality of insulating units and set to remain silent under normal working conditions and to sensibly respond to a lessening of the insulating qualities of the plurality of insulating units.

6. A high tension alternating current transmission line provided with insulators for supporting the line conductor, said insulators each comprising a plurality of insulating units and a permanent spark gap at the ground end of and in series with the plurality of insulating units and set to remain silent under normal working conditions and to sensibly respond to a lessening of the insulating qualities of the plurality of insulat ing units.

7. In a high tension alternating current transmission line, a suspension insulator, for carrying the line conductor, having a spark gap in series with the suspension insulator units.

8. In a high tension alternating current transmission line, a suspension insulator, for carrying the line conductor, having a spark gap in series with the suspension insulator units, the spark gap being located between the uppermost one of the insulator units and the supporting means from which the insulator as a whole is hung.

9. In a high tension alternating current transmission line, a suspension insulator for supporting the line conductor, and a spark gap between the line conductor and the ground in series with the suspension insulator and comprising a block of insulating material forming a spark gap bridge between the ground and the topmost one of the insulating units of the suspension insulator.

In testimony, that I claim the foregoing as my own, I have hereto affixed my signature in the presence of two witnesses.

TOMLINSON F. JOHNSON, JR.

Witnesses:

P. C. I-IEnAUL'r, A. J SMrrH. 

